352 REAGENTS AND THEIR PREPARATION [Ch. X 



Dissolve the dark red mixture in ioo cc. of 50 % alcohol. For use, 

 dilute five or tenfold with tap water. This stains best after mercuric 

 fixers. One must not collodionize sections to be stained with this, 

 as the carmine stains the collodion very deeply. Stain the sections 

 first with hematoxylin as usual; then stain 1 to 5 hours or longer with 

 the dilute mucicarmin. The mucus in goblet cells, in the mucous 

 part of the salivary glands, etc., will be red. Nuclei will be stained 

 with hematoxylin. Mount in balsam (§ 513). 



§ 550. Cedar-wood oil. — For penetrating tissues and preparing 

 them for infiltration with paraffin, thick oil is recommended by Lee. 

 For tissues fixed with osmic acid for fat the thick oil is necessary, 

 but for most histologic and embryologic work, that known as Cedar- 

 wood Oil (Florida) is excellent, also that known as Cedar-wood Oil 

 (true Lebanon). These forms are far less expensive than the thick oil. 

 The tissues should be thoroughly dehydrated before putting them into 

 cedar-wood oil, and they should remain until they are translucent. 



The thickened cedar-wood oil used for homogeneous immersion 

 should be obtained of the manufacturers of microscopes; they natu- 

 rally would supply the kind suitable for the purpose. 



§ 551. Chloroform (CHCI3). — -This is used as an anaesthetic and 

 for clearing and imbedding where fats fixed with osmic acid are to 

 be preserved in the tissues. It is also used for hardening collodion, 

 in collodion imbedding. It is an excellent solvent of cedar-wood oil 

 and is used for cleaning homogeneous immersion fluid (cedar-oil) from 

 objectives, condensers and microscopic preparations. 



§ 552. Carbol-xylene clearer. — Vasale recommends as a clearer, 



xylene 75 cc, carbolic acid (melted crystals), 25 cc. 



§ 552a. — Carbol-xylene and eosin. In order to counterstain with eosin during 

 the clearing process, the carbol-xylene is charged with eosin as follows: A saturated 

 aqueous solution of eosin is prepared, and to it is added with constant stirring, hy- 

 drochloric acid until there is a good precipitate. Filter through filter paper. Wash 

 the precipitate with distilled water until the water goes through pink. This indi- 

 cates that the acid is washed out. Dry the washed precipitate. This is soluble in 

 the carbol-xylene and enough should be added to make that pink. More or less 

 can be used depending on the depth of the eosin stain desired. That can be regu- 

 lated also by the time the sections are left in the eosined clearer. (Freeborn, Jour. 

 Ap. Microscopy, Vol. Ill, p. 1058). 



§ 553. Carbol-turpentine clearer. — A satisfactory and generally 



applicable clearer is carbol turpentine, made by mixing carbolic acid 



